JPH0368976A - Electrostatic recording device - Google Patents

Abstract

PURPOSE:To surely separate a transfer material from a photosensitive body by adding a charge for separation to the transfer material which advances between the photosensitive body and a transfer material conveying belt. CONSTITUTION:After allowing the transfer material conveying belt 501 to press- contact with the photosensitive body 1 where the toner image of three colors is formed and transferring the toner image on the transfer paper 7, fixation is executed. When the transfer material 7 advances between the photosensitive body 1 and the belt 501, the charge which has the same polarity as the surface charge of the photosensitive body 1 and is higher than the surface charge thereof is impressed on an electrode roller 503 so as to transfer toner on the photosensitive body 1 to the transfer material 7. Furthermore, by providing a conductive guide plate 509 in a paper feeding path, impressing a voltage having an opposite polarity to the roller 503 and pressing the transfer material 7 with the tip of the guide plate 509, the transfer material 7 is attracted to the belt 501 side and it is surely separated from the ejection side of the photosensitive body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic recording device that employs a belt roller transfer method for transferring a toner image from a toner image holding member to a transfer material.

[Background of the invention]

Conventionally, in the electrophotographic recording (copying) process, transfer/
Most of them used direct current or alternating current corona discharge for separation. This is because the transfer, toner adhesion amount, environmental changes, and transfer material (transfer paper) conditions are limited, and relatively stable performance can be obtained with a simple structure.

However, in cases where transfer is highly dependent on the environment, such as magnetic toner, or in processes where approximately three times the amount of toner must be transferred, such as in the case of color copying, it is difficult to apply conventional transfer methods. There was a limit.

Therefore, belt transfer methods have been studied for some time, and it was thought that high performance could be obtained in principle.

However, due to technical problems and cost considerations, there are few examples of this being put into practical use. Some systems that have been put into practical use use a high-resistance belt and a corona discharge electrode, but recently there has been a demand for strict control over ozone generation, and a system that does not use corona discharge is desired.

Therefore, the inventor of the present invention pressed an endless transfer material conveying belt toward the photoreceptor using an electrode roller, and caused the transfer material to enter between the transfer material conveying belt and the electrode roller to form a toner image on the photoreceptor. We have developed a transfer separation unit that uses a belt roller transfer method to transfer images onto a transfer material.

[Problem to be solved by the invention]

By the way, in this belt roller transfer method, it is necessary to effectively separate the transfer material from the photoreceptor, but if the transfer material remains charged with the same polarity as the transfer material conveyance belt, the repulsive force will cause the transfer material to separate. may wrap around the photoreceptor, resulting in poor separation.

An object of the present invention is to provide an electrostatic recording device having a separation transfer section that solves these problems.

[Means to solve the problem]

For this purpose, the present invention provides a conductive member to which a voltage of a polarity opposite to that of the electrode roller is applied on the transfer material inflow side of the transfer material conveyance belt, and the conductive member connects the transfer material conveyance roller with the toner image. A separation charge is applied to the transfer material that enters between the transfer material and the holder.

〔Example〕

Examples of the present invention will be described below. FIG. 1 is a diagram showing a schematic configuration of an electrostatic recording device according to one embodiment.
2 is a photoreceptor as a toner image carrier; 2 is a charging electrode; 3 is a laser beam carrying image information; 4 is a developing section comprising a yellow toner developer 4Y, a magenta toner developer 4M, and a cyan toner developer 4C; 5 is a separation transfer section, and 6 is a cleaning section.

In this electrostatic recording device, while a photoreceptor l charged at a high voltage by a charging electrode 2 rotates in the direction of arrow a, its photosensitive surface is exposed to laser light 3, thereby forming an electrostatic latent image thereon. This is then developed by a selected one of the developing devices in the developing section 4. While the photoreceptor 1 rotates three times, when laser exposure and development are performed a total of three times for yellow, magenta, and cyan images, a three-color superimposed toner image of yellow, magenta, and cyan is formed on the surface of the photoreceptor 1. is formed. During this time, the separation transfer section 5 and the cleaning section 6 are separated from the photoreceptor 1. After the three-color toner image is formed on the photoreceptor 1 as described above, the separation transfer section 5 is brought into pressure contact with the photoreceptor 1, and the three-color toner image is fed at a predetermined timing from the direction indicated by the arrow. The three-color toner is transferred onto a transfer material (paper) 7. The transfer material 7 to which the three-color toner has been transferred is fixed in a heat fixing section (not shown) and then discharged. Also, the three-color toner image is formed on the cleaning section 6. The blade 61 comes into contact with the surface of the photoconductor 1 after the photoconductor 1 is transferred, and even after the three-color toner is transferred to the transfer material 7, the photoconductor 1 remains
Remove any toner remaining on the surface.

FIG. 2 is a diagram showing the detailed structure of the above-mentioned transfer separation section 5. As shown in FIG. The transfer separation unit 5 includes a transfer material conveyance belt (501) made of an endless semiconductor, a drive roller 5O2 that supports and extends the transfer material conveyance belt 501, an electrode roller (conductive roller) 503, a tension roller 504, and an electrode roller 50.
3 is provided with a power source 505 and the like for applying a transfer electric field. The electrode roller 503 is pressed against the photoreceptor 1 by the roller 503
Application of voltage from a power source 505 to the electrode roller 503 is performed by a blade electrode 507 whose tip is in sliding contact with the electrode shaft 503b. A cleaning member 508 removes toner on the surface of the transfer material conveying belt 501 using a blade method. Reference numeral 509 denotes a conductive guide plate, which is provided in the paper feeding path, to which a voltage (ground potential in this embodiment) with a polarity opposite to the charge of the electrode roller 503 is applied, and whose tip presses the transfer material 7. It has become. 510.511 is transfer material 7
This is a transport guide.

In this transfer separation section 5, when the transfer material 7 enters the transfer material conveying belt 501 and the photoreceptor 1 with it being sandwiched,
By applying a charge having the same polarity as and higher than the surface charge of the photoreceptor 1 to the electrode roller 503 by the electric rA 505, the toner on the surface of the photoreceptor 1 is transferred to the surface of the transfer material 7.

At this time, it is necessary to prevent charge from being injected into the transfer material 7 after the charge is applied from the electrode roller 503 to the transfer conveyance bell 501 until that part is separated from the photoreceptor l. This is because when the charge is injected into the transfer material 7, an electrostatic force is generated between the transfer material 7 and the photoreceptor 1, resulting in failure of separation of the transfer material 7.

Furthermore, it is necessary to dissipate the charge to a certain level before the transfer material conveyance bell 501 completes one rotation and reaches the same position of the electrode roller 503 again. This is the transfer material conveying belt 5.
01 and the transfer material 7 or the photoreceptor 1 are separated, charges of opposite polarity to the electrode roller 503 are transferred to the transfer material conveying belt 501.
This is because it is necessary to prevent it from remaining on the surface and inhibiting the next transfer.

For this reason, the charge applied by the electrode roller 503 moves from the inner surface to the surface of the transfer material conveying belt 501 (the charge retention time constant representing the passage of time is 0.
01 to 1Qsec is appropriate.

For this purpose, in this embodiment, the electrical resistance value of the transfer material conveying bell) 501 is set to 1o10ΩcIIl to 1o1
Set to 1Ω mark, for example, about 101'Ωcm.

The material of the transfer material conveying belt 501 is such that the belt drive is stable, there is little change over time such as permanent deformation, and there is no chemical change when it comes into contact with the photoreceptor 1.
Characteristics such as high dimensional accuracy, excellent ozone resistance, controllable electrical resistance, and stable electrical properties are required. As a material that satisfies this requirement, a polymer film such as polyurethane or urethane rubber is suitable. The appropriate elastic modulus is about 450 g/l112.

Further, the surface treatment of the transfer material conveyance bell 501 is performed as follows. This transfer material conveying belt 501 has a problem in that the toner on the photoreceptor 1 adheres to areas other than the area where the transfer material 7 is placed.
It is necessary to perform cleaning using the cleaning member 508. In this embodiment, the blade type is used for the cleaning member 508 as described above for the sake of simplicity in size and structure. Therefore, the surface properties of the transfer material conveying belt 50 must be suitable for this cleaning method. Therefore, in this embodiment, the belt surface is roughened appropriately or coated with fluorine rubber, FLC, or the like.

Furthermore, the thickness of the transfer material conveying belt 501 is determined as follows. First, the voltage applied to the electrode roller 503 needs to be made approximately proportional to the thickness. This is because if the transfer material conveyance belt 501 becomes thicker, the capacitance between the electrode roller 503 and the photoreceptor l becomes smaller, and a sufficient charge cannot be applied to the transfer material conveyance belt 501. When using a rubber belt, practically 0,3x*~ln
+ is appropriate. If it is thinner than this, there will be problems such as poor manufacturing stability and difficulty in belt conveyance. In the case of a film, approximately 0.05 w to 0.5 n is practical.

Next, the material and electrical resistance value of the electrode roller 503 will be explained. First, a conductive metal such as aluminum, stainless steel, or iron is used as the material, but if a high transfer electric field is required to transfer an image with a large amount of toner adhesion, the transfer material conveying belt 501 and the photoreceptor 1 Since abnormal discharge occurs between the two and the image becomes distorted, some measures are required. This is thought to occur because the transfer material conveyance belt 501 and the photoreceptor 1 suddenly approach each other under high voltage. Regarding this point, the circumferential surface of the electrode roller 503 should be set to 105ΩCff1~
By covering it with urethane rubber, etc. with a resistance value of 10"Ω and a thickness of about 5" to prevent the electric field from rising suddenly,
It can be prevented. In the experiment, good results were obtained with a resistance value of 10"Ω0. Also, by setting the rubber hardness of this urethane rubber to 306 to 60 degrees, the transfer material conveying belt 50
The adhesion between the photoreceptor 1 and the photoreceptor 1 is improved, and the occurrence of uneven transfer can also be suppressed.

Next, the pressing force of the electrode roller 503 against the photoreceptor 1 will be explained. If this pressing force is too weak, it will cause uneven transfer and a reduction in the transfer rate; if it is too strong, letters and thin lines with a large amount of toner adhesion will tend to be crushed. Experimentally, good results were obtained with this pressing force of 10 to 1500 gf/cm, particularly 54 f g/am.

The pressing position of the electrode roller 503 on the photoreceptor I has a large effect on the separation of the transfer material 7 from the photoreceptor 1. In the belt roller transfer method, the transfer material 7 is separated into the photoreceptor 1 and the electrode roller 5.degree. 3, whichever has a smaller curvature, by its own elastic force. Therefore, it is necessary to make the curvature of the transfer material conveying bell l-501 as small as possible. In this embodiment, as shown in FIG.
is set to be upstream of position B away from the photoreceptor 1. In the experiment, the downstream end of Nisop plane A and separation position B
Good results were obtained when the distance was 2 to 4n.

Regarding this separation, it is preferable that the transfer material 7 is not placed on the transfer material conveying belt 501 side by its own weight, but is placed on the transfer material conveying belt 501 side in a suction state and separated from the photoreceptor 1. For this purpose, in this embodiment, a predetermined voltage is applied. conductive guide plate 509 to which
The conductive guide plate 509 presses the transfer material 7, thereby imparting an electric charge to the transfer material 7 with a polarity opposite to that of the electrode roller 503, thereby connecting the photoreceptor l and the transfer material conveyance. The transfer material 7 flowing between the transfer material conveying belt 5o1 and the photoreceptor 501 is electrostatically attracted to the transfer material conveying belt 5o1 so that the attraction force is stronger than that between the photoreceptor 1 and the photoreceptor l. This ensures good separation from the discharge side. Note that the conductive guide plate 509 may or may not come into contact with the transfer material conveying belt 501 when the transfer material 7 is not there. Furthermore, the charge applied to the transfer material 7 in this manner is removed as necessary after separation, as will be described later.

Next, the drive roller 502 will be explained. The drive roller 502 may be made of any material that can be manufactured with high precision, such as a solid metal roller or a rubber roller.

Next, the cleaning member 508 will be explained. As described above, since toner adheres to the surface of the transfer material conveying belt 501, if this is not removed, the back surface of the transfer material will be stained and separation failure will occur. As a cleaning method, a blade method, fur brush, etc. can be used, but
In this embodiment, a blade system using a rubber blade 508a is adopted from the viewpoints of small size, space saving, cost, etc.

To prevent the transfer material conveyance belt 501 from shifting, there are methods of providing a flange on the drive roller 502, electrode roller 503, or tension roller 504, and methods of providing a guide.According to experiments, a flange with a height of about 4 mm is effective. It was possible to obtain better performance without damaging the belt by providing it.

When the transfer material conveyance belt 501 is separated from the photoreceptor 1, when the transfer material 7 is separated from the transfer material conveyance belt 501, charges remain due to the applied separation charges. As mentioned above, this transfer material conveying belt 50
There is no particular need to remove static electricity if a suitable time constant is provided for 1, but when using a belt with a high resistance value (i.e. charge retention time constant), if static electricity is not removed, it will not be possible to properly remove the static electricity during the next transfer. Transfer electric field cannot be formed. Furthermore, if the transfer material is not properly neutralized, toner scattering will occur. As countermeasures against these problems, there are methods such as providing a static eliminating brush and using AC corona discharge, but in this embodiment, if necessary, a static eliminating brush is installed at a position after the transfer material 7 and the transfer material conveying belt 501 are separated. (not shown), or perform alternating current corona discharge from above the transfer material conveying bell) 501 and the transfer material 7 at that position (not shown).

Next, a method of driving the transfer material conveying belt 50I will be explained. The difference between the circumferential speed of the photoreceptor 1 and the moving speed of the transfer material conveyance bell 501 poses a problem as a change in the vertical magnification of the transferred image. This change in magnification is dependent on belt speed. Therefore, in order to correct this speed difference, the drive roller 50
2 needs to be controlled with high precision, but this increases costs and
This causes problems such as the durability of belts and rollers. In this embodiment, since the transfer material conveying belt 501 is pressed against the photoreceptor 1 by the electrode roller 503, a driving force is also generated on the electrode roller 503 side, and in principle, with this driving, no speed difference will occur. Become. However, the cleaning member 508
Because of the presence of such loads, slips may occur and become a problem.

Therefore, the coefficient of friction between the drive roller 502 and the transfer material conveyance bell (501) is set slightly low, and the drive roller 502
By moving the belt faster than the belt movement speed by about 0 to 1% to supplement the driving force of the electrode roller 503, the problematic speed difference could almost be eliminated.

Next, the voltage value of the voltage a505 will be explained.

The optimum value of the applied voltage varies depending on the amount of toner adhesion, the thickness and electrical properties of the transfer material 7, the thickness and electrical properties of the transfer material conveyance bell l-501, and the like. Therefore, it is necessary to decide on a well-balanced point based on the required performance and specifications of the machine. When switching the applied voltage, the thickness, physical properties, etc. of the transfer material 7 are detected by some means. In addition, when the manual feed mechanism is to be used, methods such as increasing the voltage can be considered. In this embodiment, the applied voltage is set to 3KV when paper is fed from a cassette, and when paper is fed manually, since most of the paper is thick such as OHP or envelopes, the applied voltage is set to 3KV using the manual feed signal.
(4KV). Note that the current capacity was set to a maximum of 20 μA. Of course, the voltage can also be changed by the user's input using a key or the like to print on thick paper.

By the way, when the transfer material conveying belt 501 is stretched over the electrode roller 503 by 180 degrees without using the tension roller 504, staggered repelling occurs when the transfer electric field applied to the electrode roller 503 is increased. When comparing the first and second half of the image, the occurrence of this repellent is more noticeable in the first half and less in the second half. A possible cause of these problems is that both the electrode roller 503 and the photoreceptor 1 are rollers, and the surface portion of the roller 503 and the photoreceptor 1 has a sufficient amount of air discharge in the area just before they come into contact with each other due to rotation. An electric field is formed and the toner is charged in the opposite direction. This discharge is
Actually, it is thought that this occurs between the transfer material 7 and the photoreceptor 1. As a countermeasure against this, the above-mentioned electrode roller 50
In addition to coating the surface of 3 with urethane rubber or the like having a resistance value of 10'Ω(2) to 101°Ωcm, the path of the transfer material conveying belt 501 and the transfer material 7 is changed so that a high electric field is applied immediately before transfer. The path should be set so that the electric field does not rise suddenly along the entrance path of the transfer material 7.

Therefore, in this embodiment, a tension roller 504 is disposed on the transfer material 7 entrance side of the electrode roller 503, and the transfer material conveying belt l-
501 is arranged to enter the electrode roller 503 and photoreceptor 1 from a direction close to the tangential direction of the electrode roller 503.

〔Effect of the invention〕

As described above, according to the present invention, since the inflowing transfer material is charged with a charge for separation in advance, the transfer material flowing out from the transfer portion is attracted to the transfer material conveying belt side by electrostatic force, and the toner image is There is an advantage that separation from the holder is ensured and poor separation can be prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an electrostatic recording apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing a specific configuration of a transfer separation section. 1... Photoreceptor (toner image carrier), 2... Charging electrode,
3... Laser light, 4... Developing section, 5... Transfer separation section, 6... Cleaning section, 7... Transfer material, 501
... Transfer material conveyance belt, 502 ... Drive roller, 5
03... Electrode roller, 504... Tension roller, 50
5... Power supply, 506... Elastic member, 507... Blade electrode, 508... Cleaning member, 509...
...Conductive guide plate, 510.511...Guide for transfer material.

Claims (1)

[Claims] (1) An endless transfer material conveying belt is pressed in the direction of the toner image carrier by an electrode roller, the transfer material is introduced between the transfer material conveying belt and the electrode roller, and the transfer material is placed on the toner image carrier. In an electrostatic recording device having a belt roller transfer type transfer separation section for transferring a toner image onto the transfer material, a voltage having a polarity opposite to the polarity of the electrode roller is applied to the transfer material inflow side of the transfer material conveying belt. Electrostatic recording characterized in that a conductive member is provided, and the conductive member applies a separating charge to the transfer material that enters between the transfer material conveyance roller and the toner image carrier. Device.